Paper EM2-TuM10
ZnO/LiNbO₃ Heterojunctions: A Candidate System For Multifunctional Oxides

Tuesday, November 10, 2009, 11:00 am, Room B1

Ferroelectric/semiconductor heterostructures are desirable for multifunctional devices using the charge of a ferroelectric material to manipulate the conductivity of a semiconductor. The quality of the ferroelectric/semiconductor interface is critical for maintaining a significant ferroelectric polarization charge density, and coupling this charge density into the semiconductor. Therefore, materials must have excellent chemical and structural compatibility. ZnO and LiNbO₃ may provide the desired characteristics based on the crystalline compatibility of the materials, excellent semiconducting properties of ZnO, and excellent ferroelectric properties of LiNbO₃. In this work, the structural and electrical characteristics of ZnO thin films deposited on z-cut LiNbO₃ substrates by pulsed laser deposition will be presented and compared to ZnO thin films on c-plane sapphire substrates. In all experiments, preferentially-oriented c-plane ZnO thin films were obtained based on x-ray diffraction measurements.

Hall effect measurements demonstrate a background carrier concentration in ZnO of n=2. 6x10¹⁷cm^-3 for ZnO/LiNbO₃, and an order of magnitude decrease of n=3.0x10¹⁸cm^-3 for ZnO/sapphire. Similarly, an improved electron mobility of μ=36 cm²/Vs is observed for ZnO/LiNbO₃ in comparison to μ=21 cm²/Vs for ZnO/sapphire. The reduced carrier concentration and improved mobility are attributed to a depletion layer at the ZnO/LiNbO₃ interface induced by polarization charge. The temperature dependence of electron transport in ZnO thin films will also be presented to examine the influence of polarization charge induced by the pyroelectric effect in LiNbO₃.